1. Field of the Invention
The invention relates to an audio processing apparatus, and more particularly, to an audio processing apparatus in a communication system with a microphone array.
2. Description of the Related Art
In a communication system, three components are picked up by a microphone or a microphone array, including: a source signal, interference and echo. The source signal is a desired signal, such as signals from voice, required to be sent to a far end side. Echo and interference are considered as objectionable components occurring in communication systems. The echo can be a result of a mismatch from a hybrid network, such as in the network echo case, or reflections caused by a reverberant environment, such as an acoustic echo. An echo can manifest from an originator in a speech signal, wherein the originator is able to hear his/her speech after a certain period of delay. With either kinds of echo, an annoyance factor increases as the amount of the delay increases.
Meanwhile, interference, such as environment noise, also disrupts the proper operation of various subsystems of a communications system, such as the codec. Different kinds of environment noise may vary widely in their characteristics, and a practical noise reduction scheme has to be capable of handling noises with different characteristics.
To properly remove the interference and echo picked up by the microphone array, a backend microphone array signal processing module plays an important role. For example, an adaptive beamforming filter is usually adopted in the signal processing module to beamform the source signal by suppressing the interference signal. An adaptive echo cancellation filter is also adopted to cancel the undesired echo. In addition, an automatic gain control (AGC) unit is further used in front of the signal processing module to adjust the input signal level to an appropriate level. However, as the gains of the AGC units in the microphone array diverge from one another, performance of the microphone array signal processing thereof degrades. Thus, a novel audio processing method and apparatus in a communication system with a microphone array are highly required.